1. Field of the Invention
The present invention relates to a guided vehicle system that transports articles by traveling between load ports through auto-guiding.
2. Description of the Related Art
Guided vehicles, such as overhead traveling vehicles that travel along rails in the overhead space, rail guided vehicles that travel along rails in the space near the ground, and auto-guided vehicles that travel on the floor surface without rails, transport articles between load ports. Some of these guided vehicles are equipped with a transfer device, and some are not. The load ports are sometimes called “stations”, and they may be provided, for example, at the end portion of a processing device, a stocker, an automated warehouse, or a conveyor. Articles may be temporarily placed in a buffer in the middle of transportation between the load ports.
Regarding a guided vehicle system, Patent Literature 1 (JP2006-331053) discloses that guided vehicles periodically transmit the current position and the reporting time to a controller on the ground, and the ground controller periodically carries out updating based on the transmitted data to obtain a distribution of the positions of the guided vehicles. Based on the distribution of the guided vehicles, the ground controller assigns a traveling route to each guided vehicle so as to avoid jamming. Each guided vehicle to which a traveling route has been assigned travels with a goal of arriving at the destination position (“To position”) in the shortest possible time by traveling within the range of the velocity limit and so as to avoid interference with the preceding guided vehicle. However, it is difficult to precisely estimate what position each guided vehicle passes through at what time because this depends on the jamming status of the traveling route, for example. It is thus also difficult to estimate the time at which each guided vehicle arrives at the To position. In addition, the ground controller may roughly control the future traveling amount in each portion of the traveling route by assigning a traveling route to each guided vehicle. However, it is difficult to perform control as to what guided vehicle travels at what position on the traveling route at what time.
According to Patent Literature 2 (JP2010-205102), a ground controller regularly transmits position instructions to guided vehicles, and each of the guided vehicles travels by generating a velocity instruction and a torque instruction by itself according to the received position instruction. In the system of Patent Literature 2, the positions of the guided vehicle may be controlled by the ground controller, but it is necessary to generate the position instructions at a short time interval, resulting in a great burden on the ground controller and also a high communication load on the system.